Rhodanine-based film-forming kinetic modulators unlock over 17% efficiency in all-small-molecule organic solar cells

Abstract

Controlling film morphology remains an inherent challenge limiting the performance of all-small-molecule organic solar cells (ASM-OSCs), primarily due to excessive donor-acceptor compatibility restricting further improvements. Here, we introduce a novel strategy employing rhodanine-based film-forming kinetic modulators—specifically tailored for the high-performance donor BTR-Cl—including 3-methylrhodanine (C1), 3-ethylrhodanine (C2), 3-butylrhodanine (C4), and 3-hexylrhodanine (C6). We demonstrate that the C2 modulator uniquely optimizes morphology by extending film-formation time and fine-tuning donor-acceptor miscibility, leading to enhanced molecular ordering, uniform vertical distribution, and optimal phase separation. This synergistic morphological control significantly boosts BTR-Cl crystallinity and facilitates efficient three-dimensional charge transport networks. Consequently, C2-treated BTR-Cl:N3 ASM-OSCs achieve an outstanding power conversion efficiency (PCE) of 17.12 %, ranking among the highest reported for this system. Crucially, this work introduces a novel “donor-modulator structural matching” strategy, providing a powerful new avenue for controlling film-forming kinetics to realize high-performance ASM-OSCs.